The fabrication of extremely complex, high-density integrated circuit has been made possible through advances in integrated circuit fabrication technology. Fabrication technology now exists having the capability to define circuit components having feature sizes in the sub-micron size range. For example, new lithographic techniques have been developed using X-ray and pulse-laser energy sources. Additionally, thin-film deposition technology now exists with the capability to form thin-films having precisely determined metallurgical compositions and thicknesses. Furthermore, thin-film deposition techniques have been developed which are capable of selectively depositing metals in precisely defined locations during device fabrication.
In accordance with the development of new lithographic and film deposition techniques, plasma etching technology has rapidly advanced to provide the etching capability necessary to transfer the high-resolution lithographic patterns to the underlying thin-films. The difficulty of etching a high-resolution pattern has been compounded by the development of semiconductor device components requiring multiple layers of metals having different structural compositions. Often, an etching gas ideally suited to the plasma etching of a specified metal, or family of structurally similar metals, is not effective for etching an underlying metal. This problem is most distinctly illustrated in the fabrication of metallized contact structures for high-performance semiconductor devices. For example, multi-layer metal devices are interconnected by refractory-metal via plugs. To prevent the inter diffusion of refractory-metal components, and to improve the adhesion of the refractory metal, metal adhesion layers are typically employed underlying the refractory-metal. Depending upon the material composition of the refractory-metal and the adhesion metal, completely different etching chemistries must be employed to pattern the composite metal structure.
Advanced plasma etching systems having the capability of generating different plasma chemistries are commonly employed to etch multiple layers of metal having different structural compositions. The advanced plasma etching systems have either the capability of performing plasma etching in several internal etching chambers, or provide a single etching chamber having electrical, mechanical, and gas delivery capability necessary for the generation of a variety of plasmas. Thus, advanced plasma etching equipment provides process capability to transfer high resolution patterns to multi-layer metallization structures.
While the advanced systems initially provide the capability for etching a variety of metals, this capability requires that the plasma etching systems be extremely complex. In the construction of etching chambers, a wide variety of materials are used to construct the various electrical and mechanical elements necessary for the transfer of substrates into the etching chambers. Additionally, other components such as fixtures, gas seals, and fittings, and the like, must also be present to provide complex processing capability. Many of the components internal to a plasma etching chamber are fabricated from metals having similar structural compositions to those commonly used in semiconductor devices. Additionally, many of the structural components are fabricated from polymer materials, such as high density plastics.
During the plasma etching process, the internal components of a plasma etching chamber are necessarily exposed to the reactive plasma. The chemical components of the plasma react with all surfaces exposed to the plasma, including the surfaces of the internal components of the plasma etching chamber. In addition to causing component wear, the plasma also generates particulate matter as it reacts with the internal components of the plasma etching chamber. The particulate matter is redeposited on the wall surfaces of the chamber, as well as the surface of the semiconductor substrate being etched. The particle generation and wear problems are compounded with the use of different plasma chemistries to etch the different metals present in the semiconductor device. By increasing the number of different plasma chemistries used in an etching chamber, the exposure of the chamber to plasmas having different etching characteristics results in even more wear and particulate generation. The various chemical components of the different plasmas selectively attack the various materials present inside the etching chamber.
In the fabrication of high-density semiconductor devices, it is essential that particle contamination be held to an absolute minimum. Furthermore, the processing equipment used to fabricate the devices must be available to perform etching operations on a 24 hour basis. The combination of a low particulate level and high equipment availability produces high chip-yield and reduced fabrication cycle time. To meet the need for lower particulate levels and improved equipment availability, advances in process technology are necessary for the fabrication of complex, composite metal structures.